1. Field of the Disclosure
The present disclosure relates generally to an optical system with a radiation source component and receiving fiber component separated from one another by free space. More specifically, the disclosure relates to free space high power coupler with a protective mechanism that greatly increases the damage threshold of the overall assembly.
2. Prior Art
In the prior art, relatively low powered lasers, such as those employed in optical communication or the like, emit a relatively low power radiation that is coupled into the core of an optical fiber using a lens. Certain applications require free-space propagation of radiation which then is coupled into a waveguide. Such a coupling, however, may be associated with certain difficulties, as explained immediately below.
FIG. 1 illustrates a laser system 10 configured with a source of radiation 12 emitting light along a light path. The radiation is coupled into a bulk optics 14 which focuses the received light so that it enters a core 20 of delivery fiber 16.
Even if delivery fiber 16 is a single mode standard waveguide, not all light from bulk optics 14 is coupled into a core 20 of fiber 16. A portion of light is typically guided in a cladding 28 which is highly optically-transmissive, i.e., only a small portion of light, if at all, is absorbed. The component absorbing the light is coating or adhesive 26.
Once high power light in the order of a watt or higher is coupled into delivery fiber 16 and transmitted through cladding 28 to coating 26, high temperatures, which inevitably accompany the absorption by the coating, may detrimentally affect the latter that, as well known, has a relatively low optical damage threshold. The coating 26 is used for protecting glass fibers from a mechanical damage and provides delivery fiber 16 with the desired degree of ruggedness. Hence, if coating 26 is damaged by elevated temperatures, the glass—material of fiber 16—can be irreparably damaged as well. Thus, typically, coating 26 is rather the limiting factors for the maximum power handling of system 10.
Still a further undesirable consequence of the elevated temperatures is associated with a volume of material 24 configured to couple delivery fiber 16 to a mount 22 during assembly of system 10 and selected from the group consisting of adhesives, epoxy and a combination thereof. Typically, material 24 has an optical damage threshold lower than the fiber coating. Should the energy of light portion, propagating in cladding 28 of delivery fiber 16, couple first into cladding 28, which has a high coefficient of heat conduction, into volume of material 24, the latter tends to melt. As a consequence, the coupling between mount 22 and delivery fiber 16 deteriorate. A further undesirable consequence of the melted adhesive is that it may migrate to the ends of the optical fiber and absorb radiant energy from the light source, resulting in local hot spots that can damage the optical fibers. As a result, adhesive/epoxy 24, like protective coating 26, may be the factor limiting the power requirements applied to modern fiber laser system.
A need, therefore, exists for an optical system configured to reliably operate at high power levels.
A further need exists for an optical system configured with a fiber receiving unit which has a structure that does not substantially limit the power handling capabilities of the fiber laser system.
Still another need exists for a rugged fiber receiving unit configured to receive and guide high power radiation, which is received through free space, without substantial power losses.
Still a further need exists for a rugged fiber receiving unit configured to minimize thermally induced structural damages by high power radiation to its components.